Protective device.



J. D. HOFFMAN.

PROTECTIVE DEVICE.

APPLICATION FILED SEPT.21,1909.

l on Patented June 21, 1910.

'Anonzw 1 www co PHOTO-UTHOGRAPHE UNITED STATliLS PATENT OFFICE.

JESSE D. HOFFMAN,

OF DUKE, OKLAHOMA, ASSIGNOR OF ONE-HALF TO NANCY L. 4

BURROW, OF DUKE, OKLAHOMA.

PROTECTIVE DEVICE.

Specification of Letters Patent. Patented J 11119 21, 1910.

Application filed. September 21, 1909. Serial No. 518,880.

To all whom it may concern:

Be it known that I, Jnssn D. HOFFMAN, a citizen of the United States,residing at Duke, in the county of Jackson, State of Oklahoma, haveinvented certain new and useful Improvements in Protective Devices; andI do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to a protective device for use in telephonesystems to protect the instruments contained therein from damage bytrespassing high pressure currents Which may be introduced into thesystem in various ways such as from lightning or crosses with highpressure circuits.

To this end the invention consists in a self-contained protective devicewhich may be readily introduced into a system of the type heretoforementioned by connection with a line Wire and ground wire.

The object of the invention is the construction of a protective deviceof the character named which will be efficient in use and comparativelyinexpensive to manufacture, install and maintain.

With the above and other objects in view the invention consists in thearrangement and combination of parts to be hereinafter more particularlydescribed and pointed out in the claim.

In describing the invention in detail reference will be had to theaccompanying drawings in which like characters of reference denote likeparts in the several views, and in which,

Figure 1 is a view in elevation of the invention with the cover thereofin section and showing same connected with a line wire of a telephonesystem and with a supplemental ground wire; and Fig. 2, a plan view ofthe device with the connection between same and the line Wire of atelephone system omitted.

Referring to the drawings, 1 represents a base plate of insulatingmaterial, having secured thereto transversely thereof conducting plates2 and 3, 1 and 5, said plates being arranged in spaced parallel pairswith their lower ends bent at an angle whereby they may be secured tothe base plate 1, through the medium of the screws 6, 7, 8 and 9 respectively; the portion of said screws projecting above the base plate 1being threaded to receive the binding nuts 10, 11, 12 and 13respectively, for a purpose to be hereinafter described. The said plates2 and 3 have their upper ends flared outwardly with respect to eachother and the plates 4: and have their upper ends similarly flared andeach pair of said plates is so arranged and mounted that they convergeslightly toward eachother in the direct-ion of their free ends.

Between the plates 2 and 3 are inserted the carbon blocks 14 andseparating these blocks is a strip of mica 14: having an opening 15therethrough to form an air space between the blocks 14. Correspondingcarbon blocks 16 are inserted between the plates 4; and 5 and are inturn separated from each other by a strip of mica 17 provided with anaperture 18 to form an air space between said blocks 16. A spheroidalcover 19 secured upon the base plate 1 serves to inclose the elements ofthe device heretofore mentioned and protect same against dust andmoisture. Mounted centrally of said plate 1 and extending in a verticaldirection is a conducting rod 20, the upper end of which pierces thecover 19 and is threaded above and below said cover to receive a nut 22traveling on the threaded portion below and a nut 2& on the threadedportion above, said cover 19. An electrical connection 30 has one endsecured in contact with the rod 20 and the other secured in contact withthe screw 7 by means of the nut 11, while another electrical connection31 has one end secured in contact with the rod 20 by means of the nut 22and the other end in contact with the screw 8 by means of the nut 12. Itwill thus be obvious that the rod 20, connection 30, and plate 3 areelectrically connected as are also rod 20, connection 31 and plate 1.

Mounted in the cover 19 and located on each side of the rod 20 andextending in a vertical direction parallel to said rod are the doubleend binding posts 25 and 26 each of which extends through the cover 19and has its ends threaded. A nut 27 is mounted for travel on thethreaded lower end of the post 25 and a nut 28 similarly mounted on itsupper end, while a nut 29 is mounted for travel on the lower end of thepost 26 and a nut 32 mounted for travel on the upper end thereof. Anelectrical connection 23 has one end secured in contact with the bindingpost 25 by the nut 27 and the other end secured in contact with thescrew 6 by the nut 10. Another electrical connection 34: has one endsecured in contact with the post 26 by the nut 29 and with the screw 8by the nut 13; thus electrically connecting the plate 2, the connection23 and the post 25, and again the plate 5, connection 3d and the post26. The line wire is represented as at L and the service wire as at S,and the instrument in the service wire as at J. The line wire L iselectrically connected with the post 25 by the nut 28, and the servicewire S is also electrically connected with the post 25 through the sameagency. Another extension of the line wire is connected with the bindingpost 26 by the nut 32, and the other end of the service wire S is alsoconnected to the post 26 by the nut 32.

The operation of the device is as follows :assu1ning that a normalcurrent is passing through the line L in the direction of the arrow inFig. 1, it will take the following course :first entering the bindingpost 25, then through the service wire S, through the instrument J,through the binding post 26 and then again out through the line wire.However, it a high pressure current is trespassing the line L as theresult of a lightning discharge or momentary crossing with high pressurecircuits, such as electric light or power circuits, said high pressurecurrent will pass through the line wire L, through the binding post 25,through the electrical connection 23, through the plate 2, across thecarbon blocks let, jumping the air space formed by the aperture in thestrip of mica separating said carbon blocks, then through the plate 3,connection 30, the rod 20 and out through the connection 35 to theground. It will thus be obvious that the instrument J, located in theservice line is thus thoroughly protected from injury by trespassinghigh currents in the main line.

What is claimed is A protective device of the character described,comprising a base plate, a spheroidal cover mounted on said base plate,a plurality of pairs of spaced plates mounted on said base plate beneathsaid cover, a pair of electrodes inserted between each pair of platesand connected with its adjacent plate, the members of each pair ofelectrodes being separated by a perforated insulating material, abinding post for each pair of plates mounted on said cover adapted forelectrical connection with a line wire and with one plate of itsrespective pair; a vertical rod disposed between said pairs of platesand having its lower and upper ends threaded and projecting through thebase plate and cover respectively, the threaded portion of the upper endof said rod being disposed both above and below the cover, a nut mountedon the threaded lower end of the rod adapted to bear against the endface of the base plate, a nut mounted on the threaded upper portion ofthe rod disposed above the cover for electrical connection with asupplemental ground wire and a nut mount ed on the threaded portion ofthe upper end of the rod disposed beneath the cover for electricallyconnecting the rod with the other plate of each pair.

In testimony whereof, I afiix my signature, in presence of twowitnesses.

JESSE D. HOFFMAN. lVitnesses F. L. Bumcow, (at. C. MADDEN.

